The present invention relates to a control valve for automatically maintaining a constant rate of flow of a fluid through a pipeline.
In almost every branch of industry pipeline systems for fluids, such as water or gases, are in use. Varying amounts of such fluids are removed from the pipeline systems, and this leads to pressure fluctuations within the system. In order to control the flow rate of the fluid through the pipeline so that the flow rate remains constant, it has been required to provide manual control valves or regulating devices which are controlled by means of measuring instruments. When such measuring instruments are employed however, the pipeline on both sides thereof must be maintained straight. To obtain optimum operating behavior of the pipeline systems, it is necessary to conduct lengthy, frequently inaccurate adjustment procedures for small plants, and larger plants can be adjusted only with costly regulating devices. In order to maintain a constant flow through a pipeline system, it therefore disadvantageously is necessary first of all to measure the flow and then to pass on information from such measurements to a control valve which is opened or closed as necessary. This requires auxiliary equipment.
It also has been proposed to employ a rigid diaphragm disk and a rubber or other compressible regulating disk arranged in a control valve consecutively in the direction of flow, to attempt to automatically maintain constant a fluid flow rate. Under the pressure of the fluid and with axial displacement, the rigid diaphragm disk is pressed against the regulating disk, as a result of which the cross section of a flow opening in the regulating disk is varied, depending on the pressure difference across the control valve. This type of control valve however does not maintain a satisfactorily constant flow and cannot be used for certain media, particularly aggressive media which would adversely effect the material, such as rubber, of the regulating disk. Furthermore, such material of the regulating disk is subject to aging, so that with time the function of the control valve suffers.